@charset "utf-8" ;
body,html{
    height: 100%;
}
.box{
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    height: 100%;
}
/* 头部 */
.top{
    height: 57px;
}
.main{
  height:1px;
  flex-grow: 1;
  background-color: black;

}
.footer{
    height: 50px;
    background-color: aqua;
}